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TOPIC: Sharpness Testing Jig

Sharpness Testing Jig 8 months 1 week ago #13214

  • wickededge
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I finally got around to building one of these machines as designed by BassLakeDan, per the specs on his page here: How Sharp is It. The instructions are complete and easy to follow and the machine works great! I am really excited to extend our research by adding in the extra, crucial information provided by this machine. I'm hoping others will take heart from how easy I found the build to be, set up one of their own and start posting data. The more we can share data that has been standardized about exactly how sharp our blades are getting via different geometries, finishes and techniques, the more we'll all learn in a hurry. I know that 'sharpness' is a very broad topic and means many different things to many people. In this instance we're only examining 'point sharpness' as defined by Dan. A good example of how we can use this technology is to test the effects of stropping: to strop or not to strop; how much to strop; should we strop at the same angle at which we sharpened? etc... Another way to use it is to find the point of diminishing returns on the number of strokes to make with a given grit. Yet another that comes to mind is how much pressure we apply with the stones (you could put your sharpener on a scale and measure the force you're using and then test the edge with various levels of force applied.) It's a very exciting tool to have in the shop. Here are some pictures:

h5a0ba6f.jpg


h446d5d7.jpg
--Clay Allison
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Sharpness Testing Jig 8 months 1 week ago #13215

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I'll clean it up a little and build a holder for the battery and buzzer and find a way to tidy up the wires. Then I'm gonna get started testing!
--Clay Allison
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Sharpness Testing Jig 8 months 1 week ago #13219

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Nice Job Clay. Will be interested to see the results when you start testing.
Do you have an estimate on what you have into the project in time and money?
Phil

MAX 2001-2013
Hoping there is that bridge!
I miss you Buddy!
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Sharpness Testing Jig 8 months 1 week ago #13226

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Pretty cool! :woohoo:

Since you built one... maybe you could answer this. Do you think, instead of a scale, attaching a ruler (or using a rod with marks) where the weight slides, and recording that would be as accurate? If so, if it could be rigged up to test a knife that was still clamped in the WE... that would be interesting.... an easier and much quicker way to "test as you go", especially if you want to test all the variables you mentioned.

Nice job!
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Sharpness Testing Jig 8 months 1 week ago #13229

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PhilipPasteur wrote:
Nice Job Clay. Will be interested to see the results when you start testing.
Do you have an estimate on what you have into the project in time and money?

The build took about 2 hours at a nice casual pace. I spent about an hour and maybe $75 collecting the supplies though I probably could have done it a lot cheaper by using spare plywood and such. I also bought full packs of washers and nuts instead of using stuff I had laying around so could have shaved some money there.
--Clay Allison
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Sharpness Testing Jig 8 months 1 week ago #13230

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cbwx34 wrote:
Pretty cool! :woohoo:

Since you built one... maybe you could answer this. Do you think, instead of a scale, attaching a ruler (or using a rod with marks) where the weight slides, and recording that would be as accurate? If so, if it could be rigged up to test a knife that was still clamped in the WE... that would be interesting.... an easier and much quicker way to "test as you go", especially if you want to test all the variables you mentioned.

Nice job!

As designed, it is in essence a single beam scale. I added a second rod to slide my weights (because they were hard to slide smoothly on the ridged main beam,) making it a double beam scale. You could easily add another rod on the other side of the main beam to make it a true triple beam scale. From there, I think you could use a postal scale to set up the notches for the weights on each beam. You'd start with the biggest increments on one beam, find and mark the places at even weight intervals by watching the scale as you slide the weights down the beam. Once you have those set, you'd do the same for next beam with smaller weight increments and the same with even smaller increments for the last beam. I was getting results of 200g-225g yesterday, so maybe the large beam would use weight increments of 50g, the middle could use increments of 10g and the smallest increments of 1g. You'd have to build in a zero point to show when the scale is zeroed out. You would need one reference point on the beam and one on the rod supporting it.
--Clay Allison
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Sharpness Testing Jig 8 months 1 week ago #13231

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Hey Clay,
Where did the weight set that you are using come from? It looks like a set for a "real" balance scale.
They look lots better than the fishing weights...
Phil

MAX 2001-2013
Hoping there is that bridge!
I miss you Buddy!
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Sharpness Testing Jig 8 months 1 week ago #13233

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PhilipPasteur wrote:
Hey Clay,
Where did the weight set that you are using come from? It looks like a set for a "real" balance scale.
They look lots better than the fishing weights...

I got them off of Amazon: Slotted Weight Sets
--Clay Allison
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Sharpness Testing Jig 8 months 1 week ago #13234

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Clay,

Excellent job on the jig construction ! I particularly like your improvements to the weight slide bar.

As your time permits, please keep us informed as to the results you get with the jig, and if you have any data sheets of test results. Because of your extensive experience with the practical world of sharpness, I would be most interested to hear if feel that the jig provides:

1.) data that seems to make sense to your feeling about a series of blades and sharpening techiniques. In other words give us a "reality check" on the numeric feedback that the jig provides vrs "expected results"

2.) is the jig providing you an ability to look at a "finer granularity" when appraising the sharpness of a blade over your previous methods (whatever they might have been i.e. paper slicing or whatever) and is the numeric results of practical benifit that offsets the time of using the jig.

3.) your thoughts about possible new test media for the jig

Again, great that you finally, on your busy schedule, were able too put one together !

Best Regards - Dan
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Sharpness Testing Jig 8 months 1 week ago #13236

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Clay,
Thanks for the link to the weight set. It looks like it would be easier to manipulate than the fishing weights, especially with the second beam in place.

I tried looking closely at the pictures, but I could not figure it out. How did you attach the second beam to the main arm? Maybe some rubber tubing just taped in place ??

I am getting interested...
:)
Phil

MAX 2001-2013
Hoping there is that bridge!
I miss you Buddy!
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